Dozens of protesters marched outside the posh Warwick hotel yesterday before the arrival of Mahmoud Ahmadinejad — with one prancing around in a gigantic paper-mache head mocking the Iranian dictator.

“Keep Ahmadinejad out of New York!” some chanted, while others held signs outside the Midtown hotel.

The Holocaust-denying president — who claims the United States orchestrated the Sept. 11 terrorist attacks — is expected to arrive at the Warwick today and stay until at least Wednesday, when he is scheduled to address the UN General Assembly.

Protesters say they’re angry that a luxury Manhattan hotel would play host to a man whose country has been criticized for its repressive treatment of its people and who has supported terrorist groups such as Hamas.

“The Warwick might be hard up for business these days, but damaging its reputation and angering New Yorkers will come back to bite it,” said Nathan Carleton, a spokesman for United Against Nuclear Iran, which plans to demonstrate outside the hotel on Monday.

“It is outrageous that The Warwick would accommodate a terrorist regime in exchange for its illegitimate money, and not even admit it,” Carleton said.

Security is going to be tight at the West 54th Street hotel, sources said. Law-enforcement snipers will be stationed on rooftops surrounding the hotel and those entering will be patted down.

“People here [in New York] hate this guy,” a hotel source told The Post yesterday. “It wouldn’t surprise me if someone made an attempt at his life.

“If you leave and come back, you get patted down again,” the source added. “We can’t take any chances.”

Cement barriers blocked curbs to keep vehicles from parking and two NYPD squad cars were stationed near the entrance.

Meanwhile, the hotel continues to receive shipments to prepare Ahmadinejad’s room — which he insists on being custom-tailored.

Hotel staffers wouldn’t give up any of the details.

“It’s all very hush-hush,” one said. “The fewer people know what’s going on, the better.”